adding effects like smoke
Not to take anything from @Kristof Meirlaen's answer, I take a more simplistic approach -

An easy way overall is to texture a 2D plane in the 3D window with the video of the pot, or preferably, make it the background image/video.  If it is made the background don't forget to increase it's opacity to 100% in that background image panel.

Back in the 3D window, texture another 2D plane with an "Alpha Layered" (See below) video for the poof-of-smoke.  You have to set the smoke plane to start at the desired Blender frame number so it doesn't start up until required.  This is done in the texture properties under the "Image tab" -->"Start".(bottom left of the tab)  Enter the required "BLENDER TIMELINE" frame number where the smoke video is to start.

You'll also need to tick the "Auto Refresh" box to make it play the video.

On the premise that you are using the background image option, view it from the camera so you'll see the pot.  Align the camera so the smoke is positioned exactly as desired. 

Render it all with the Open GL renderer for speed, or Blender's internal renderer if you like watching the grass grow!  (Top left of 3D window under the "Render" drop down menu.

The anim here took me 45 mins, and admittedly a quick and dirty example.  It was started from scratch, pot, particles, smoke and bubbling liquid all created in Blender.  The smoke puff was as described above however, a "Cumulous cloud" made with Blender's cloud generator and saved as an alpha layered pic to be textured onto a 2D plane.  The plane was animated. (scaling, rotated etc)

Hope this gives you something to start from...

  

PS:  You mention that you're new so some info - 
To align the camera whilst viewing through it, select the camera (right click on it), press N, ---> open the "View" tab and tick "Lock to camera view".

You can then use the mouse and buttons to move/rotate/zoom the camera to wherever you like as you would a first person view in a game.

Don't forget to untick that box again, or you could lose the smoke's alignment with the background image.

Further hint - if your machine does as mine does occasionally, starts rendering in solid mode, hit escape, and start the render again.  The 2nd attempt usually works properly.

If you don't have a "Smoke-poof" video, an "Alpha Layered" image might do.  Just animate the 2D plane that it's texturing, by increasing it's size (scaling) from nothing to maximum over a few frames and move the entire plane upwards. Once it's at a decent size,  make it rotate a little, or even shrink back to nothing if that suits. The smoke's shape can also be distorted and bent in various stages by doing that to the 2D plane.

Making a puff of smoke is a simple matter in Blender.  Start with the cube, scale it up a little and press T to bring up the Tools panel at left.  Open the "Create" tab and at the bottom, press "Cloud Generator".   This will open up a small menu.  Tick 'Particles', then select Cumulous from the list, press "Generate cloud" button.

A cube inside your original cube will appear with what looks like a clog of black cotton inside that.  Press F12 to render it as a good looking cloud!  

The pic is taken from the 3D window's camera so it should be lined up fairly well.  If not adjust the view as mentioned above.

To give the cloud's outer edges "fluffiness" and make it's surrounding background invisible, we have to add transparency. We do this by rendering it with an alpha layer.  

Goto the right hand properties panel (SH-SPACE), select the camera icon near the top. (2nd from left) and after setting it's output dimensions and folder etc,  goto the "Shading" tab and change the Alpha setting to "Transparent".

In the "Output" tab, select the format at left to PNG, compression to about 15$ and at the right, click on it's RGBA box. (The A is for alpha)

In the timeline set the frames to start at 1 and end at 1 also.  This will produce a .png alpha layered pic file in your nominated output folder.

From the 3D window press "N" to bring up the viewport's parameters.

Open the "Display" tab, tick "Only Render" and "World Background". 
Press N again to close the panel

Go back up to the top left of the 3D window's Render Drop-down and click on "Render animation".  We have to use Blender's internal render in order to get a proper cloud pic.

At this point you can make a cup of tea/coffee while it renders the cloud.  It does a good job though.

This can be your smoke "poof" image which can be coloured, shaded, distorted, shaped and animated any way you like.

The pic shows how Cu clouds can look in their original form.  This pair was made to sail lazily across an alien sky.